A large number of thin film transistors (TFTs), pixel electrodes, and scan lines and data lines across each other are fabricated by processes of depositions, photolithography and etching to form a pixel array on a first glass substrate. In order to provide voltages and signals for activating the TFT in each pixel unit, patterns of electrical circuits are formed on the first glass substrate to electrically connect the pixel array and micro devices on the periphery of the first glass substrate. By this way, timing controller and source drive integrated circuits (ICs) disposed around the first glass substrate and the gate driver IC constructed on the side of the first glass substrate can respectively transmit data signals and scan signals to each pixel unit through the patterns. A color filter and a common electrode layer are formed subsequently on a second glass substrate. In the process of assembling a display panel, the second glass substrate with the color filter and common electrode layer attached thereon is reversed to face the pixel array on the first glass substrate. Thereafter, a liquid crystal (LC) layer is sandwiched between the second and first substrates.
Because the LC layer cannot emit lights by itself, a backlight unit is disposed opposite to the display panel to provide light to the liquid crystal display for displaying images. For example, the backlight unit of a small-scale liquid crystal display (LCD) comprises a light-guide plate, films, a reflector and a light emitting diode (LED). The light-guide plate is preferably an acrylic plate made by injection molding. The LED is constructed at a side of the light-guide plate. Lights emitting from the LED enter the light-guide plate through an edge thereof and transmit to another end of the light-guide plate by total internal reflection. The reflector is opposite to the light-guide plate to avoid light leaking from the surface of the light-guide plate. Further, in order to enhance the uniformity of the light illuminating the surface of the light-guide plate, a brightness enhanced film (BEF) and a diffuser are generally constructed upon the light-guide plate, wherein the diffuser is used to diffuse the lights and the BEF is used to focus the lights.
Referring to FIG. 1, a construction of a display panel 1 and a backlight unit 2 according to the prior art is shown. As described above, the display panel 1 comprises a first glass substrate 10. On the first glass substrate 10 is a displaying area 11 comprising of a second glass substrate and a liquid crystal layer. A source driver IC 12 and a gate driver IC 13 are respectively mounted on the first glass substrate 10 around the displaying area 11 to control a pixel array within the displaying area 11. Generally, an extending flexible printed circuit (FPC) 14 is fabricated at the side near the source driver IC 12. Back-end of the FPC 14 is connected to the source driver IC 12 and the gate driver IC 13 through the circuit layout on the first glass substrate 10, whereas the front-end of the FPC 14 is connected to the system for transmitting controlling signals thereof to the display panel 1.
It is noted that another extending FPC 21 is mounted on an internal sidewall of a casing of the backlight unit 2 for the purpose of providing power to the LED within the backlight unit 2. As shown in the figure, the front end of the FPC 21 is connected to the FPC 14 by welding. Thus, the power from the system is transmitted to the LED through the FPC 14. Now a typical design of the LCD is used as an illustration. A welding area 141 is usually defined on the FPC 14 for the electrical contact of the FPC 21 while assembling the display panel 1 and the backlight unit 2.
It is noted, however, there are serious drawbacks at the electrical contact of the FPC 14 and the FPC 21. Referring to FIG. 2, when the assembling of the display panel 1 and the backlight unit 2 has been accomplished, the assembly will subsequently be accommodated into a casing of a system (e.g. PDA, digital cameras, mobile phones, handheld PC or the like). At this time, the FPC 14 and the FPC 21 are generally folded downward so as to allow the whole assembly to be inserted into the casing of the host system and enable the FPC 14 to be received in a slot, which electrically connect to the interior of the system. Thus, signal connection is built. Under the condition described herein, the welding area 141 on the FPC 14 increases the thickness of the FPC 14. Accordingly, the difficulty in folding the FPC 14 is elevated while assembling. Further, the FPC 21 easily peels off and separates from the welding area 141 of the FPC 14 when the FPC 14 and the FPC 21 connecting at the welding area 141 are folded and bended simultaneously.
In practice, the rate of the short circuit derived from separation between the FPC 14 and FPC 21 is about 5% to 10%. Hence, it is important to seek solutions for solving the problems existing in the present process.